Luminous flux, measured in lumens (lm), is defined as a quantity of energy of light emitted per second in all directions. In some systems, the amount of luminous flux emitted by light emitting diode (LED) devices or LED modules may be controlled through various dimming techniques.
For example, some systems may perform digital dimming of an LED device or module by varying the duty cycle of a pulse width modulation (PWM) control signal that is used to drive the LED device. Such a system may vary the duty cycle to cause a proportional variation to the amount of luminous flux associated with the LED device. In addition, or as an alternative to performing digital dimming techniques, some systems may perform analog dimming of an LED device by controlling the amount of forward current provided to the LED device. An adjustment to the amount of forward current associated with an LED device may induce a proportional adjustment to the amount of luminous flux associated with the LED device.
In any case, no matter the technique used to perform LED dimming, most systems require tight control of over their respective dimming parameters (e.g., duty cycle, amount of forward current, or other parameters) to satisfy the luminous flux requirements of a particular application. For example, most automotive lighting applications are required to operate over a wide temperature range (e.g., 40° C. to 115° C.). If performing digital dimming, a PWM engine of an automotive lighting application may need to dynamically adjust the PWM duty cycle (e.g., by plus or minus percent) to compensate for temperature changes so as to maintain a steady amount of luminous flux. Maintaining such tight control over the PWM duty cycle may be challenging for some systems, particularly those systems where an expensive microcontroller driven PWM engine is not an option.